高原湖泊微藻和微量金属元素的相互作用过程及实验模拟研究

微量金属元素的微藻生物地球化学主要通过研究微藻与微量金属元素的各种相互作用，在时空上了解微藻在微量金属元素的分布、迁移和富集等过程中所起的作用，以及由此引起的微藻本身的成分、结构、形态和功能在不同地球化学环境中的变异等。地球化学环境变化及由此产生的生态环境效应是目前研究的科学热点之一。工业革命以来，人为活动强烈地改变了地球表层的局部乃至全球的微量金属元素含量，对生物的正常生长乃至人类的健康构成了潜在的威胁。作为初级生产力，浮游藻类在水生生态系统中占有重要地位；它通过生物积累、光合作用及生物矿化，驱动着C、N、Si、P、O、，S、Fe等元素在水体内部的生物地球化学循环；微藻对环境变化敏感，能够很好的响应微量金属元素生物地球化学行为的变化。目前有关湖泊微量金属元素地球化学及浮游植物生态学的研究较多，但浮游植物和微量金属元素相互作用规律的系统研究较少，对湖泊微量金属元素复杂的生物地球化学行为的解释仍缺乏实验依据。本论文研究了高原湖泊阿哈湖、百花湖和红枫湖的微量金属元素和微藻的时空分布特征，探讨了两者之间的相互关系；研究了小球藻和衣藻对微量金属元素的生物吸收和生物吸附特征：研究了微量金属元素对微藻生理生化因子（生长速度和碳酸醉酶胞外酶）的影响；分析了微藻和微量金属元素的相互作用规律，为湖泊微量金属元素生物地球化学行为的解释提供科学依据。通过上述研究，获得了以下几点认识：1．阿哈湖、百花湖和红枫湖的微藻生物量在2002年出现了两个高峰，一个在春季，一个在秋季；这是水温、光照、营养源和捕食等多种因素综合作用的结果。百花湖和红枫湖的微藻以蓝藻和绿藻为主；阿哈湖的微藻春季以蓝藻和绿藻为主，秋季以硅藻为主。阿哈湖和红枫湖的叶绿素a含量在垂直方向随深度增加呈下降趋势，表层浮游藻类较多。2．阿哈湖、百花湖和红枫湖2002年过滤水中微量金属Co、Ni、Cu、zn、M。含量的月变化各不相同；其变化是微藻和降水等多种因素综合作用的结果。降水（酸雨）腐蚀湖泊流域的碳酸盐岩，其中的微量金属元素被溶解，随河流输入湖泊，影响了微量金属元素在湖水中的含量（如三个湖中的cu，阿哈湖中的Mo）。百花湖和红枫湖的蓝藻和绿藻的生物量变化与微量金属元素C。、Cu、zn、M。的含量变化正相关，可能是因为这些微量金属元素在某些程度上限制了蓝藻和绿藻的生长；阿哈湖的硅藻的生物量变化与微量金属元素的含量变化负相关，可能是由于硅藻对它们的富集造成了两者之间的负相关关系。浮游藻类通过吸附、吸收和富集溶解态微量金属元素，影响其在垂直方向的分布。溶解态微量金属元素在垂直方向的分布趋势并不完全相同，其垂直分布特征是本身的浓度大小、浮游藻类和湖底微生物等诸多因素共同作用的结果。3．微藻对微量金属元素生物吸附的平衡时间因对微藻处理方式的不同而不同。单离子体系和多离子体系中衣藻对同一微量金属的吸附情况不同，多离子体系中微量金属元素对吸附作用位点的相互竞争造成了这种差异。多离子体系中，死藻细胞对Cd、zn、cu、Co、Mn的吸附量的大小顺序与它们的原子量的大小顺序一致，这可能是在各种微量金属元素的相互竞争中，死的藻细胞优先选择原子量大的金属；活藻细胞对Cd、Fe、C。、Zn（Ni）的吸附量的大小顺序与它们的离子密度的大小顺序正好相反，这可能是由于活的藻细胞的生物调节作用使其优先选择离子密度小的金属。4．在单离子体系和多离子体系中，不论是活的藻细胞还是死的藻细胞，小球藻对各种微量金属的吸附量大于或相当于衣藻的吸附量；小球藻和衣藻对各种微量金属的吸附量一般随金属浓度的升高而增大。在单离子体系中，衣藻和小球藻对每种微量金属的生物吸收速度随浓度的变化趋势相似，一般是随金属浓度升高吸收速度先增加后减小，但增加和减小分界线处吸收速度对应的金属浓度大小各不相同；小球藻和衣藻对Mn、Fe、C。、Cu、zn（藻必需的微量金属营养元素）的吸收速度大于对Ni、Cd的吸收速度；这主要是因为同一藻类维持新陈代谢所需各种金属的量不同，对不同微量金属毒害的承受程度（生物调节能力）也不同；不同藻类对同一微量金属的需求量和毒害的承受程度也不相同。在单离子体系小球藻和衣藻对各种微量金属的吸附和吸收中，随着浓度的增加，吸收过程比吸附过程更快的达到饱和状态。5．各种微量金属对小球藻和衣藻生长的影响情况因金属种类和藻的种类的不同而不同。Cd·Cu、Ni、zn对小球藻和衣藻生长的毒害较大，而且对衣藻的影响比小球藻的影响大·随各种微量金属浓度的增加，小球藻和衣藻生长速度的变化趋势一般表现为先增大后减小，和它们对各种微量金属的吸收速度的变化趋势一致：可见吸收到藻细胞体内的微量金属的量和它们对细胞生长的影响有密切．的关系，藻细胞的生物调节在这个变化趋势中起了重要的作用。6．阿哈湖和红枫湖微藻碳酸醉酶胞外酶活性明显高于衣藻的CA。活性，主要是因为c入的活性与环境中HcO3一的浓度有关。cd、zn、cu和Pb对微藻c人的活性的抑制效应因金属浓度的不同而不同，而且抑制作用因微藻种类的不同而不同。微量金属元素对CA活性的影响主要通过三个途径：①．直接与CA这一含zn蛋白酶作用；②．间接影响藻细胞内CAe的新陈代谢：③．直接改变cA。的生物活性（例如Pb）。低浓度的Fe、Mn、Co 、Ni和cd刺激了衣藻碳酸配酶胞外酶（cAe）的活性，高浓度的各种金属抑制cAe的活性；cu和zn对衣藻cAe的抑制作用比其它金属离子的强。衣藻对Fe和Mn影响CAe的生物调节作用明显，其次是Co和Ni。7．微藻是影响高原湖泊微量金属元素地球化学行为的重要因素，影响情况因微藻种类而有所差异。微藻能强烈地改变环境中微量金属元素的含量，微量金属元素含量的变化也影响了微藻的生理生化功能。微藻和微量金属的相互作用因微藻和金属种类的不同而不同；这种种类差异性是造成微量金属元素生物地球化学行为复杂性的主要原因之一。

黄土风化过程中元素的地球化学行为及风化淋滤模拟实验

开展黄土风化淋溶规律方面的工作，在土壤改良，环境质量评价，黄土高原的开发和治理，生态环境的保护等方面均有一定的理论和实际意义。笔者旨在从剖面上、地球化学动力学、水化学、及微量元素重金属形态方面研究黄土风化过程中元素的地球化学行为。一、黄土风化成壤作用过程中常量、微量元素的地球化学行为 本文的样品主要采自陕西洛川黑木沟黄土剖面，并选择了以Ti作为难迁移参考组分的方法从定量的风化程度指标和元素的淋失或聚积指标反映元素风化过程的变化。二、黄土与古土壤中重金属的存在形态及风化成壤作用对其影响 结果表明：Fe、Cu、Zn、Co、Ni均在残余态含量最高，其次为晶形和无定形氧化铁结合态，黄土与古土壤中晶形、无定形氧化铁含量与和这两个形态结合的Cu、Zn、Co、Ni之间作线性回归分析表明，Cu、Zn、Co、Ni与晶形、无定形氧化铁之间分别存在显著正相关。由各形态计算的相对淋溶、聚积值表明：黄土风化为古土壤后，碳酸盐结合态的重金属几乎全部释放。而晶形、无定形氧化铁结合态的重金属则明显聚积，其它形态的重金属变化不大。因此黄土风化为古土壤后与晶形、无定形氧化铁结合的重金属含量增加是古土壤相对黄土重金属总量增加的主要原因。三、黄土风化淋滤模拟实验及动力学机理 结果表明：1）pH对黄土风化有显著影响，酸度愈强，愈易于风化作用的进行；2）母质对黄土风化也有影响。四、洛河水系仙茹河流域元素的水迁移序列 为了反应在目前的水热生物气候条件下元素的迁移情况，笔者由仙菇河的河水化学组成及该流域黄土的平均化学成分，计算了粉砂质黄土带元素的水迁移序列：Na > Mg > Ca > K > Si > Fe > Al。

微束分析在滇黔桂地区油源对比及演化研究中的应用

油源对比及有机质演化成熟度的研究是石油地质勘探中极为重要的部分。文中运用同步辐射X－射线荧光分析、离子控针和显微激光拉曼探针等多种现代微束分析技术，通过“单盲”测试性质的预研课题“微束分析在油源对比方面的应用”进行了方法研究，建立以有机质中微量元素（尤以过渡族元素V, Ti, Cr, Mn, Fe, Ni, Cu, Zn为主）的分布模式和有机官能团组成作为主要判别指标，综合考虑个别特征元素来进行油源对比研究的方法，取得了良好的结果；应用显微激光拉曼控针研究有机质的演化成熟度，更为科学、准确地反映了有机质的演化程度，并与镜质体反射率 Ro 之间建立了良好的线性关系：S = 0.8511 + 0.4004Ro。通过研究证实了微束分析技术用以油源对比研究在方法上是可行的。并在此基础上又以广西十万大山盆地为例进行了应用研究，结果表明油源岩为采自盆地东部的G－7，不同于以往认为的G－5，为石油地质的研究提供了新的方向。

Effect of Nb Content on the Microstructure and Mechanical Properties of Zr-Cu-Ni-Al-Nb Glass Forming Alloys

(Zr65Al10Ni10Cu15)(100-x) Nb-x glass forming alloys with Nb contents ranging from 0 to 15 at.% were prepared by water-cooled copper mould cast. The alloys with different Nb contents exhibited different microstructures and mechanical properties. Unlike the monolithic Zr65Al10Ni10Cu15 bulk metallic glass, only a few primary bee beta-Ti phase dendrites were found to distribute in the glassy matrix of the alloys with x = 5. For alloys with x = 10, more beta-phase dendrites forms, together with quasicrystalline particles densely distributed in the matrix of the alloys. For alloys with x = 15, the microstructure of the alloy is dominated by a high density of fully developed P-phase dendrites and the volume fraction of quasicrystalline particles significantly decreases. Room temperature compression tests showed that the alloys with x = 5 failed at 1793 MPa and exhibited an obvious plastic strain of 3.05%, while the other samples all failed in a brittle manner. The ultimate fracture strengths are 1793, 1975 and 1572 MPa for the alloys with x = 0, 10 and 15 at.% Nb, respectively.

Metallographic Analysis of Cu-Zr-Al Bulk Amorphous Alloys with Yttrium Addition

Minor yttrium addition can improve the glass-forming ability of Cu-Zr-Al ternary alloys via suppression of the growth of eutectic clusters. Yttrium addition also makes the room temperature ductility of the alloys decrease, and both the compressive strength and elastic strain limits increase slightly.

Influence of Forced Convection on Columnar Microstructure During Directional Solidification of Al-Ni Alloys

This paper presents a summary of cellular and dendritic morphologies resulting from the upward directional solidification of Al - Ni alloys in a cylindrical crucible. We analysed the coupling of solid-liquid interface morphology with natural and forced convection. The influence of natural convection was first analyzed as a function of growth parameters (solute concentration, growth rate and thermal gradient). In a second step, the influence of axial vibrations on solidification microstructure was investigated by varying vibration parameters (amplitude and frequency). Experimental results were compared to preliminary numerical simulations and a good agreement is found for natural convection. In this study, the critical role of the mushy zone in the interaction between fluid flow and solidification microstructure is pointed out.

Effect of Carbon Addition on Microstructure and Mechanical Properties of Ti-Based Bulk Metallic Glass Forming Alloys

A kind of novel Ti-based composites was developed by introducing different amounts of carbon element to the Ti-50 Cu-23 Ni-20 Sn-7 bulk metallic glass forming alloys. The thermal stability and microstructural evolution of the composites were investigated. Room temperature compression tests reveal that the composite samples with 1% and 3% (mass fraction) carbon additions have higher fracture strength and obvious plastic strain of 2 195 MPa, 3.1% and 1 913 MPa, 1.3% respectively, compared with those of the corresponding carbon-free Ti-50 Ni-20 Cu-23 Sn-7 alloys. The deformation mechanisms of the composites with improved mechanical properties were also discussed.

Comparative Study Of The Influence Of Natural Convection On Directional Solidification Of Al-3.5 Wt% Ni And Al-7 Wt% Si Alloys

We present numerical simulations of thermosolutal convection for directional solidification of Al-3.5 wt% Ni and Al-7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al-7 wt% Si, but not in Al-3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

Theory Of Phase Transformation And Reorientation In Single Crystalline Shape Memory Alloys

A constitutive model, based on an (n + 1)-phase mixture of the Mori-Tanaka average theory, has been developed for stress-induced martensitic transformation and reorientation in single crystalline shape memory alloys. Volume fractions of different martensite lattice correspondence variants are chosen as internal variables to describe microstructural evolution. Macroscopic Gibbs free energy for the phase transformation is derived with thermodynamics principles and the ensemble average method of micro-mechanics. The critical condition and the evolution equation are proposed for both the phase transition and reorientation. This model can also simulate interior hysteresis loops during loading/unloading by switching the critical driving forces when an opposite transition takes place.

Atomistic investigation of the effects of temperature and surface roughness on diffusion bonding between Cu and Al

Molecular dynamics (MD) simulations are carried out to analyze the diffusion bonding at Cu/Al interfaces. The results indicate that the thickness of the interfacial layer is temperature-dependent, with higher temperatures yielding larger thicknesses. At temperatures below 750 K, the interface thickness is found to increase in a stepwise manner as a function of time. At temperatures above 750 K, the thickness increases rapidly and smoothly. When surface roughness is present, the bonding process consists of three stages. In the first stage, surfaces deform under stress, resulting in increased contact areas. The second stage involves significant plastic deformation at the interface as temperature increases, resulting in the disappearance of interstices and full contact of the surface pair. The last stage entails the diffusion of atoms under constant temperature. The bonded specimens show tensile strengths reaching 88% of the ideal Cu/Al contact strength. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Synthesis, spectral, and thermal characterizations of Ni(II) and Cu(II) beta-diketone complexes with thenoyltrifluoroacetone ligand

Two kinds of nickel(II) and copper(II) P-diketone complexes derived from thenoyltrifluoroacetone ligand with blue-violet light absorption were synthesized by reacting free ligand and different metal(II) ions in sodium methoxide solution. Their structures were postulated based on elemental analysis, ESI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films on K9 glass substrates were prepared using the spin-coating method. Their solubility in organic solvents, absorption properties of thin film and thermal stability of these complexes were evaluated. (c) 2006 Elsevier B.V. All rights reserved.